/* bit search implementation
 *
 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * Copyright (C) 2008 IBM Corporation
 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
 * (Inspired by David Howell's find_next_bit implementation)
 *
 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
 * size and improve performance, 2015.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <seminix/bitops.h>
#include <seminix/bitmap.h>
#include <seminix/kernel.h>

#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
        !defined(find_next_and_bit)

/*
 * This is a common helper function for find_next_bit, find_next_zero_bit, and
 * find_next_and_bit. The differences are:
 *  - The "invert" argument, which is XORed with each fetched word before
 *    searching it for one bits.
 *  - The optional "addr2", which is anded with "addr1" if present.
 */
static inline unsigned long _find_next_bit(const unsigned long *addr1,
        const unsigned long *addr2, unsigned long nbits,
        unsigned long start, unsigned long invert)
{
    unsigned long tmp;

    if (unlikely(start >= nbits))
        return nbits;

    tmp = addr1[start / BITS_PER_LONG];
    if (addr2)
        tmp &= addr2[start / BITS_PER_LONG];
    tmp ^= invert;

    /* Handle 1st word. */
    tmp &= BITMAP_FIRST_WORD_MASK(start);
    start = round_down(start, BITS_PER_LONG);

    while (!tmp) {
        start += BITS_PER_LONG;
        if (start >= nbits)
            return nbits;

        tmp = addr1[start / BITS_PER_LONG];
        if (addr2)
            tmp &= addr2[start / BITS_PER_LONG];
        tmp ^= invert;
    }

    return min(start + __ffs(tmp), nbits);
}
#endif

#ifndef find_next_bit
/*
 * Find the next set bit in a memory region.
 */
unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
                unsigned long offset)
{
    return _find_next_bit(addr, NULL, size, offset, 0UL);
}
#endif

#ifndef find_next_zero_bit
unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
                 unsigned long offset)
{
    return _find_next_bit(addr, NULL, size, offset, ~0UL);
}
#endif

#if !defined(find_next_and_bit)
unsigned long find_next_and_bit(const unsigned long *addr1,
        const unsigned long *addr2, unsigned long size,
        unsigned long offset)
{
    return _find_next_bit(addr1, addr2, size, offset, 0UL);
}
#endif

#ifndef find_first_bit
/*
 * Find the first set bit in a memory region.
 */
unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
{
    unsigned long idx;

    for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
        if (addr[idx])
            return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
    }

    return size;
}
#endif

#ifndef find_first_zero_bit
/*
 * Find the first cleared bit in a memory region.
 */
unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
{
    unsigned long idx;

    for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
        if (addr[idx] != ~0UL)
            return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
    }

    return size;
}
#endif

#ifndef find_last_bit
unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
{
    if (size) {
        unsigned long val = BITMAP_LAST_WORD_MASK(size);
        unsigned long idx = (size-1) / BITS_PER_LONG;

        do {
            val &= addr[idx];
            if (val)
                return idx * BITS_PER_LONG + __fls(val);

            val = ~0ul;
        } while (idx--);
    }
    return size;
}
#endif

#ifdef __BIG_ENDIAN

/* include/linux/byteorder does not support "unsigned long" type */
static inline unsigned long ext2_swab(const unsigned long y)
{
#if BITS_PER_LONG == 64
    return (unsigned long) __swab64((u64) y);
#elif BITS_PER_LONG == 32
    return (unsigned long) __swab32((u32) y);
#else
#error BITS_PER_LONG not defined
#endif
}

#if !defined(find_next_bit_le) || !defined(find_next_zero_bit_le)
static inline unsigned long _find_next_bit_le(const unsigned long *addr1,
        const unsigned long *addr2, unsigned long nbits,
        unsigned long start, unsigned long invert)
{
    unsigned long tmp;

    if (unlikely(start >= nbits))
        return nbits;

    tmp = addr1[start / BITS_PER_LONG];
    if (addr2)
        tmp &= addr2[start / BITS_PER_LONG];
    tmp ^= invert;

    /* Handle 1st word. */
    tmp &= ext2_swab(BITMAP_FIRST_WORD_MASK(start));
    start = round_down(start, BITS_PER_LONG);

    while (!tmp) {
        start += BITS_PER_LONG;
        if (start >= nbits)
            return nbits;

        tmp = addr1[start / BITS_PER_LONG];
        if (addr2)
            tmp &= addr2[start / BITS_PER_LONG];
        tmp ^= invert;
    }

    return min(start + __ffs(ext2_swab(tmp)), nbits);
}
#endif

#ifndef find_next_zero_bit_le
unsigned long find_next_zero_bit_le(const void *addr, unsigned
        long size, unsigned long offset)
{
    return _find_next_bit_le(addr, NULL, size, offset, ~0UL);
}
#endif

#ifndef find_next_bit_le
unsigned long find_next_bit_le(const void *addr, unsigned
        long size, unsigned long offset)
{
    return _find_next_bit_le(addr, NULL, size, offset, 0UL);
}
#endif

#endif /* __BIG_ENDIAN */
